This study assessed temporal variability in elemental composition (As, Cd, Pb, Cu, Fe, Zn, Mn, K, C, and N), stable isotopes ( δ 13 C and δ 15 N), and the C:N ratio in Sargassum horridum over decadal, intra-annual, and inter-annual periods. It also identified factors influencing the accumulation of toxic elements (As and Cd) and assessed potential human health risks associated with S. horridum consumption. Sampling included spring collections in 2011 and 2022 at three sites in La Paz Bay, and seasonal sampling at one representative site between 2020 and 2022. Decadal changes were evaluated using the full dataset, while inter- and intra-annual variability was assessed using the seasonal time series. The results showed significant decreases in As, Cu, Zn, K, C, and the C:N ratio from 2011 to 2022, while δ 15 N increased. The ANOVA revealed significant inter- and intra-annual variability and year-month interactions in elemental composition, indicating temporal variability in bioaccumulation patterns. Arsenic accumulation was mainly associated with K, N, year, and δ 15 N, whereas Cd was related to δ 13 C, δ 15 N, and Zn, suggesting different accumulation mechanisms. The human health risk assessment indicates that dietary exposure to S. horridum exceeds U.S. EPA reference dose-based safety thresholds for As, with THQ values of 0.45–1.86 (5 th –95 th percentiles from Monte Carlo analysis), indicating that it is unsuitable for human consumption without prior treatment to reduce arsenic content. This study enhances our understanding of elemental bioaccumulation dynamics in brown macroalgae and supports informed decisions regarding the use of S. horridum as a food resource. • Long-term increase in δ 15 N suggests changes in anthropogenic inputs. • Elemental variability across months and years should be considered for monitoring • K, N, Zn, year, δ 13 C, and δ 15 N, explain As and Cd variability in S. horridum • As poses a health risk, limiting S. horridum consumption without prior treatment
Mazariegos-Villarreal et al. (Sun,) studied this question.